1. Field of the Invention
The present invention relates to a data receiver, a data transmitter, an information processing method, and a computer program, more particularly to a data receiver, a data transmitter, an information processing method, and a computer program for performing communications of an video signal or a control signal.
2. Description of the Related Art
HDMI (High Definition Multimedia Interface) is known as an interface standard for inputting and outputting a digital video and an audio. HDMI is the interface standard mainly aimed for inputting and outputting the digital video and the audio for a household appliance or an AV device. In particular, it has a configuration that DVI (Digital Visual Interface) of a digital interface used for connecting a personal computer with a display is further developed to transmit and receive a video signal, an audio signal, and a control signal together by one cable. A transmission side apparatus for performing contents transmission in compliance with a HDMI standard is referred to as a HDMI source and a contents receiving side apparatus is referred to as a HDMI sink.
In HDMI, TMDS (Transition Minimized Differential Signaling) which is a digital transmission system for a display video signal employed for DVI is used for a physical layer, and high-speed digital data transmission may be realized. TMDS is one of the means differentially transmitting the digital data, and includes links consisting of four channels in total for transmitting three types of video signals R (Red)/G (Green)/B (Blue), and a reference clock signal. Each video signal performs serial conversion on parallel signal of a 10-bit, and transmits 10-bit data per clock cycle. For example, if a clock is set to 500 MHz, 5G bit video data can be sent per a second (effective transmission rate of HDMI ver1.3 is 250 Mbps to 3.4 Gbps).
TMDS is a digital data transmission style which causes a pair of electric conductors, such as a twisted pair cable, to transmit the clock and NRZ (Non Return to Zero) data as differential signals. This type of transmission system has an advantage in that it is strong against variations in potential difference of a transceiver, can eliminate extraneous noises by common-mode voltage removal action, and can suppress unnecessary radiation. The transmission system can also be used for a high speed data transmission for a comparatively long distance of approximately 10-100 m.
Further, HDCP (High-bandwidth Digital Content Protection) is used as a contents protection system, such as illegal copy prevention of digital contents outputted and inputted by application of TMDS. In order to transmit the safe contents, before starting the contents transmission, an authentication process including a common process of an encryption key is performed between the transmitter (source) and a receiver (sink) of the contents. The authentication process is performed through a bidirectional bus set up in a HDMI interface, i.e., an IIC line referred to as DDC (Display Data Channel). By applying the encryption key shared between the transmitter and receiver in the authentication process, a contents transmission side (source) encrypts transmission contents to be outputted to a receiving side (sink). The receiving side (sink) decodes and reproduces the encrypted contents received from the transmitting side by using the encryption key.
Furthermore, in the HDMI standard, a CEC (Consumer Electronics Control) line which is a two-way communication line between the transmitter (source) and the receiver (sink) is set to transmit user operation information on the transmitter (source) side or receiver (sink) side to a HDMI device via a CEC line, allowing various processes to be performed. For example, a power supply of TV is turned OFF by a remote control unit of TV being a receiver (sink), to realize “all-off” in which a power supply of a device connected to a HDMI terminal is also turned OFF. Further, contents replay is started on a video side and a power supply of a target device, such as TV, AMP, etc. is turned ON to realize one-touch play for switching to a connected HDMI input.
For example, the receiver (sink) as a contents reproduction device, such as TV can be connected with the transmitter (source) which is an apparatus for providing various contents. In particular, the apparatus includes a DVD player, a video tape-recorder, a tuner, etc. According to the HDMI standard, the transmitter (source) which is set to be selected by the receiver (sink) can obtain the information stored in a device information storing memory (EDID-ROM) provided to the receiver (sink). However, when the source is not in the selection state, the source in the non-selection state cannot obtain the information in the device information storing memory (EDID-ROM) of the sink. The device information storing memory (EDID-ROM) has stored therein resolution information of the contents which can be reproduced in the receiver (sink), signal format information which is accepted by a display, and the like. for example. When performing a process of transmitting the contents, the contents selection and data processing are performed in accordance with this information.
Further, a physical address (Physical address) which is required in order to perform the data communications is recorded in the device information storing memory (EDID-ROM) of the receiver (sink). The transmitter (source) obtains the physical address from the device information storing memory (EDID-ROM) of the receiver (sink), and performs an address mapping process enabling communications through HDMI. This address mapping is performed by using the CEC line which is the two-way communication line between the transmitter (source) and the receiver (sink) as described above.
As described above, however, according to the HDMI standard, the transmitter (source) which is not set to be selected by the receiver (sink) cannot obtain the information stored in the device information storing memory (EDID-ROM) provided to the receiver (sink), therefore the communications cannot be performed between the transmitter (source) which is not set as the selection state, and the receiver (sink) via the CEC line. In other words, the address mapping process, the all-off by means of the CEC, the one-touch play, etc. cannot be used at all.